the FSS is fine as long as you are using a decent oil like M1 0W40 or similar. The most important part to make sure is running temperature, make sure the engine gets hot and toasty before ramping on it.

The sump capacities of these engines are nearly twice the usual similar sized engine. Hence it can take a while to beat down the oil - a really long while with a nice oil.

I have noticed that with synthetics the oil gets dark but the engine casings are very clean. I think its just the nature of it.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

The oil gets dark because it keeps all the engine filth suspended rather than depositing it through the engine....

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

FWIW from my oil analysis tech: "I would not rely on monitors. They can't take into account nitration levels from exhaust gases, and also oxidation."

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Well, send your oil sample in for analysis, as suggested by several others.

I probably will just once, to play it on the safe side.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Looks like my driving habits will have the FSS letting me go 12,000 miles or so before an oil change. Interesting. I'll do an OA at 8,000 to see how I'm doing.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

After reading Terry Allison's posts, with the same model/engine car as you and I drive/drove, I don't see any problem with that.

I got to worrying about the paper MB filter holding-up (not disintegrating) over time, (in my 3-year or 10K mile oil change schedule) a lot more than I did about the Mobil 1. Mobil 1 is to me a Godsend of oils to use, IMO.

Thats what I like.

btw my drive changed for a month and the FSS took that into account and forced me to change the oil - total run 13280 miles on the diesel rated oil I put there.

The fleece filter I used was a special kind of dark as sin black and dirty when I removed it. The oil was really nasty too but as it dripped away in the oil pan some seeped on the sides of the sump near the drain hole and I saw that the oil stain was clean on the sides and it was holding the brown stuff captive in it.

This time the oil of selection was Castrol 5W40 syntec with MANN fleece filter. Till now the oil is clean as can be.

The engine still sounded perfect even with the dirty oil. Keeping this in mind I think the FSS is sensible. I think I should pull an oil sample midway next time and hand over to a lab.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)